The Working of a Shock Absorber

By | April 21, 2014

Shock absorbers are important part of your car. They keep your driving safe. It is, therefore, important to know the working of shock absorbers. Imagine your car without shock absorbers. When your car rolls on a bumpy part of the road, you will get the feel as if you are shaken. To prevent such situations, shock absorbers are necessary. The shock absorber controls the suspension system in a vehicle by dampening the suspension springs. It does so by providing resistance to uncontrolled bouncing motion created by the spring. A hydraulic fluid is used for the purpose.

What a shock absorber is all about?
A shock absorber is basically an oil pump situated between the car frame and the wheels. There are two mounts, the upper and the lower mounts connected to the frame and the axle respectively. And inside, the upper mount is connected to a piston inserted into the tube filled with a hydraulic fluid. The piston contains very small orifices for the fluid to seep through, but since the orifices are very small, this happens only under high pressure.

When the vehicle passes over a bump in the road, the springs exert force on the upper mount. Since only part of the hydraulic fluid goes from the tube through to the outside of the piston, the up and down movement becomes dampened and slow.

This further forces the spring to move slowly thereby restricting uncontrollable bouncing. Further, a reserve tube around the circumference of the hydraulic tube that contains extra fluid. There are two cycles in the suspension process. That is, compression and extension.

Compression
Compression occurs as the piston moves downward, pushing against the fluid in the chamber below it.

Extension
Extension is when the piston moves upwards pressing against the fluid in the chamber above the piston.
As said earlier, since the upper mount in connected to the sprung mass, that is the frame along with the body, compression results in order to support and control the body of the car, and the lower mount controls the non-sprung mass that is the wheels. Compression is more in amount compared to extension because the weight of the sprung mass is always more than the weight of the non-sprung mass.

Struts
A strut is another common dampening structure. In the strut, the spring is not outside its body but, rather it is mounted into the spring. Struts perform two functions, dampening and vehicle stability. Struts don’t support the vehicle weight, but only determine the speed at which weight is transferred to the body of the vehicle

Anti-sway bars
Anti-sway bars reduce vehicle sway especially in turns. What it does is, it spans around the entire axle and joins the suspension from one to the other. So in case of a body roll, or when the body moves up and down, it transfers motion from one wheel to the other. This creates a more stabilized and leveled ride. Even for vehicles that don’t have anti-sway bars, there are kits using which it can be easily mounted.

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